1. Field of the Invention
This invention relates to an automatic fill water level control device and an overfill drain device for use with a swimming pool to obtain a desired pool water level. More specifically, the invention relates to a dual tank arrangement that is in communication with a pool and contains an adjustable automatic fill device and an overfill drain device in a fixed relationship to each other, so that setting the level of one of the devices automatically sets the level of the other device.
2. Description of Related Art
Conventional pools contain overfill drains constructed as follows. A drain pipe is placed in the pool wall at the height of the desired water level, which may be coincident with a scupper extending within the pool wall below the upper extent thereof. The drain pipe terminates either on the land surrounding the pool or into a nearby drain. Leaves and other debris floating on the pool water surface can plug the outlet hole in the pool wall, compromising the efficiency of the overfill drain and causing overflow conditions. A recent innovation in pool design is the vanishing edge pool, in which the water level is intended to coincide with the upper extent of the pool wall, and a drain channel is provided outside the pool wall and below the upper extent thereof. The pool water appears to be uncontained and thus creates an arresting visual presence. However, water level control is critical to achieving this effect without squandering a large volume of water flowing over the pool edge. The simple drain pipe of prior art pools cannot be used in a vanishing edge pool, due to the fact that there is no pool wall extending above the water level in which to mount the drain opening.
Thus, for a vanishing edge pool it is essential to maintain tight control on the water level of the pool; i.e., with ⅛ inch tolerance. In particular, the water fill level and the water drain level must be spaced vertically to a very close dimension to avoid unnecessary waste of water while keeping the water level coincident with the upper edge of the pool wall. One prior art apparatus, described in U.S. Pat. No. 7,003,817, provides an automatic fill device for a pool, and an overfill drain device, both supported on a common structure that is adjustable vertically. This arrangement enables adjustment of both the fill level and drain level in one operation, and prevents misalignment of those two levels that can cause overfill conditions or insufficient water levels.
The incoming water to the automatic fill device is typically provided at high pressure, either from city water mains or from a pump (well pump, pool pump, etc.). A float valve senses water level and opens and closes a high pressure valve to add water to the tank when the level falls. Generally, the float must move a few inches to actuate the valve and open it fully. As a result the water level set by the float valve varies in accordance with the float position, and accordingly fluctuates up and down by a factor of a few inches. This fluctuation may be acceptable in a standard pool, but in a vanishing edge pool this sort of ebb and flow repeatedly exposes the top edge of the pool wall and spoils the stunning visual effect of the vanishing edge pool.